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Alpha-2-Delta Ligand — Neuropathic Pain / Epilepsy Adjunct Pregnancy: Avoid if possible — neonatal withdrawal reported; register with UK Epilepsy and Pregnancy Register if used for epilepsy

Gabapentin

Brand names: Neurontin

Adult dose

Dose: Neuropathic pain: 300 mg on day 1, 300 mg BD day 2, 300 mg TDS day 3; Epilepsy adjunct: 300 mg TDS initially
Route: Oral
Frequency: 3 times daily
Max: 3600 mg/day (epilepsy); 3600 mg/day (neuropathic pain — though 1800–2400 mg/day often sufficient)
Titrate over 3–7 days to reduce tolerability issues. Doses >1800 mg/day: non-linear absorption — split into 3 equal doses. Avoid abrupt withdrawal (seizure risk in epilepsy; also rebound pain and anxiety). Class C controlled drug in UK (Schedule 3) since 2019 — 28-day prescribing limit; no repeat prescriptions without new prescription.

Paediatric dose

Dose: 10 mg/kg on day 1, 10 mg/kg BD day 2, 10 mg/kg TDS day 3 mg/kg
Route: Oral
Frequency: 3 times daily
Max: 35–70 mg/kg/day (age-dependent); seek paediatric neurology guidance
BNFc: licensed from 6 years for focal seizures; neuropathic pain — specialist use only in children

Dose adjustments

Renal

Significant renal adjustment required — CrCl 30–59: max 1400 mg/day BD; CrCl 15–29: max 700 mg/day once daily; CrCl <15: 300 mg on alternate days; haemodialysis: supplemental doses post-dialysis

Hepatic

No dose adjustment required — not hepatically metabolised

Paediatric weight-based calculator

BNFc: licensed from 6 years for focal seizures; neuropathic pain — specialist use only in children

Clinical pearls

  • Gabapentin and pregabalin reclassified as Schedule 3 Controlled Drugs (UK) in April 2019 — MHRA alert following misuse and diversion, particularly in opioid-dependent patients
  • Non-linear pharmacokinetics above 1800 mg/day — saturable intestinal absorption; split doses maximise bioavailability
  • In the neurology context: used as adjunctive AED for focal seizures, and for neuropathic pain in MS, post-herpetic neuralgia, diabetic neuropathy
  • Pregabalin (linear kinetics) has more predictable dose-response and is licensed for generalised anxiety — often preferred for neuropathic pain
  • Renal dosing is critical — accumulation in renal failure causes severe encephalopathy

Contraindications

  • Hypersensitivity to gabapentin
  • Acute pancreatitis (caution)

Side effects

  • Somnolence (very common)
  • Dizziness
  • Ataxia
  • Fatigue
  • Peripheral oedema
  • Weight gain
  • Nausea
  • Blurred vision
  • Behavioural changes (children)
  • Respiratory depression (especially with opioids, benzodiazepines)
  • Abuse potential and dependence

Interactions

  • Opioids — synergistic respiratory depression (MHRA 2017 warning — gabapentinoids increase opioid-related death risk)
  • Benzodiazepines — additive CNS and respiratory depression
  • Morphine — increases gabapentin levels
  • Antacids — reduce gabapentin absorption (separate by 2 hours)
  • Alcohol — additive CNS depression

Monitoring

  • Renal function (dose adjustment)
  • Respiratory function (especially if co-prescribed opioids)
  • Mood and behaviour (especially children)
  • Weight
  • Seizure diary (epilepsy use)

Reference: BNFc; BNF 90; MHRA 2019 Gabapentinoids Controlled Drug Classification; MHRA 2017 Opioid/Gabapentinoid Respiratory Depression Warning; NICE CG173 (Neuropathic Pain). Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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